Textile finishing agents that improve the dyeability of cellulose fabrics are known. Among these are quaternary ammonium compounds derived from tertiary amines and epichlohydrin, and having the reactive group ##STR1## Dvorsky et al., U.S. Pat. No. 4,499,282.
These known compounds are characterized by the formula EQU [Y--M--Y[.sup.k+ k/rX.sup.r- FORMULA Ia,
or by the formula EQU [Y--M.sup.k+ --Y].sup.k+ k/rX.sup.r- FORMULA Ib,
where Y is a reactive group as defined above, r is an integer of 1-3; k is an integer of 1 or 2; X is an anionic residue of a strong inorganic or organic acid; and M is a residue derived from a heterocycle with two nitrogen atoms. (These formulas for the quaternary ammonium compounds are the same, except that Formula Ib shows the location of the k+ charge.) The compounds of Formula I are used to finish cellulose fibers; they greatly improve the dye fastness of substantive dyes, and also somewhat improve the fastness of anionic and other reactive dyes.
After dyeing it is necessary to remove excess dye and ancillary chemicals by washing, a time-consuming process that requires large amounts of water and energy. With some dyes it is necessary to increase the fastness of the dye to prevent subsequent bleeding. One method of improving fastness is to create a complex between the dye molecule and a macromolecular compound having an opposite charge.
Washing and fastness are particularly important and complex when dyeing and printing cellulose fibers with reactive dyes. When a reactive dye is used to color a cellulose fabric, only one active site reacts with the fiber. A relatively large portion of each dye molecule hydrolyzes and must be removed. Dye and print fastness therefore depends to a large degree on the efficiency of the washing process: the more hydrolyzed dye that is removed, the better the washing process.
Many solutions have been sought with regard to the problems of dyeing and washing when reactive dyes are used. With regard to the dying compounds themselves, specific dyes and dyeing conditions have been sought which maximize the binding of dye molecules to the fabric fibers, and thus minimize the amount of excess hydrolyzed dye to be removed by washing. Another solution would be to select bifunctional dye molecules and achieve dyeing conditions which promote the removal of the excess hydrolyzed portion after dyeing. In such a scheme, the active portion of the dye molecule binds firmly to the fibers, while the excess portion is bound less firmly to the active portion and is easily released during washing.
Various washing technologies are also known. One method relies on the use of a suspension of solid sorbents. This method, however, is expensive and relatively inefficient. Another method relies on cationic agents applied after washing. The purpose of the agent is to block the dye residues which remain after washing. This method, as heretofore known, has suffered from a serious disadvantage: the fastness of the dye when exposed to light is impaired.